Adiabatic smear bands in a Ti-6Al-4V titanium alloy

Dynamic (gamma approximate to 10(3)/sec) torsional experiments were performed to investigate the process of initiation and formation of adiabatic shear bands in Ti-6Al-4V alloy. In this study, thin-wall tubular specimens were deformed dynamically in a torsional Kolsky bar (torsional split Hopkinson bar). Through high-speed photography of a grid pattern previously printed on the specimen's outer surface, the local strain and the local strain rate were found to be in the range of 75%-350% and 8.0 x 10(4)/sec, respectively. The width of the shear bands ranged from 12-55 mu m. In addition, an array of infrared detectors was employed to measure the local temperature rise during the deformation process. A peak temperature of 440-550 degrees C was found in the various tests. The fracture surface of the shear band material was characterized by (1) regions of elongated dimples within which no second phase particles were observed, and (2) regions with a relatively flat and smeared appearance. There was no clear evidence based either on the appearance of the shear band in SEM or the measured temperature rise to suggest that the material within the shear band had undergone a phase transformation. (C) 1998 Elsevier Science Ltd. All rights reserved.